This application is based on Japanese Patent Application No. 2002-5931 filed on Jan. 15, 2002 the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a fuel injection system for an internal combustion engine.
2. Description of Related Art
Usually, in a multi-cylinder type diesel engine (hereinafter referred to as xe2x80x9cenginexe2x80x9d), there occurs engine vibration due to an engine revolution speed change in each combustion stroke in each cylinder which is caused by variations in combustion power between the cylinders. Particularly, in an unloaded state of the engine, i.e., in a stable idling state, vibration and noise of the engine may offend a driver. It is known that an engine revolution speed change between cylinders in the engine occurs due to variations in fuel injection amount and combustion factor in the engine between cylinders which are caused by a difference between individual injectors for cylinders.
In view of this point and for the purpose of diminishing an engine revolution speed change between cylinders to decrease engine vibration in the whole of the engine there has been conducted a non-uniform fuel amount compensating control. In the non-uniform fuel amount compensating control, an engine revolution speed change in each combustion stroke in each of the engine cylinders is detected and the fuel injection amount is adjusted to an optimum injection amount for each of the cylinders so as to smooth the engine revolution speed change between the cylinders. According to the non-uniform fuel amount compensating control, when a cylinder-by-cylinder injection correction amount updating (reflecting) condition is existent, an engine revolution speed change in each combustion stroke in each engine cylinder is detected and the detected value is compared with a mean value of engine revolution speed changes in all the cylinders, then the injection correction amount for each cylinder is updated so as to smooth the engine revolution speed change between the cylinders. The updated value of the injection correction amount is stored to compensate the fuel injection amount for each of the engine cylinders. This control is also called as a FCCB learning control or a FCCB control and the cylinder-by-cylinder injection correction amount updating condition is also called as a FCCB condition.
However, in a fuel injection system employing the FCCB control, when the FCCB condition has changed from existence to non-existence, the injection correction amount for each cylinder of the last time in the condition existence is held until the FCCB condition revives. But, in case of a change of the temperature environment, including engine temperature and/or fuel temperature, during non-existence of the FCCB condition, giving rise to a difference in engine revolution speed change between cylinders. Therefore, there arises the problem that engine vibration offends the driver until the injection correction amount for each cylinder is again updated after the FCCB condition revives.
It is an object of the present invention to provide a fuel injection system that is capable of compensating an engine operating condition change during the FCCB condition was not established.
It is another object of the present invention to provide a fuel injection system capable of suppressing engine vibration from an initial stage in the case where the FCCB condition was not existent last time but is existent this time.
According to the invention, when the FCCB condition has been existent from the last time, an engine revolution speed change in each cylinder is detected based on both a maximum engine revolution speed and a minimum engine revolution speed in each combustion stroke in each cylinder. Subsequently, a deviation of the engine revolution speed change in each cylinder is calculated based on both the detected value of the engine revolution speed change in each cylinder and a mean value of engine revolution speed changes in all cylinders.
Then, in accordance with the deviation of the engine revolution speed change in each cylinder, an injection correction amount for each cylinder is updated so as to smooth the engine revolution speed change between cylinders. Two temperature conditions, which are an engine temperature detected by an engine temperature detecting means and a fuel temperature detected by a fuel temperature detecting means are inputted. The injection correction amount for each cylinder updated by a correction amount updating means is stored in a correction amount storage means as an injection correction amount for each cylinder corresponding to the two temperature conditions.
When the FCCB condition was not existent last time but is existent this time, an initial injection correction amount for each cylinder is calculated based on the injection correction amount for each cylinder stored in the storage means in accordance with the two temperature conditions. The initial injection correction amount is obtained based on present values of the engine temperature and the fuel temperature.
Therefore, even if the temperature environment had been changed while non-existence of the FCCB condition, the FCCB control can be resumed on the basis of the initial injection correction amount for each cylinder. Since the initial injection correction amount has been stored in accordance with the temperature condition, it is possible to suppress engine vibration and noise of the engine.
According to another aspect of the present invention, the FCCB control for smoothing the engine revolution speed may be performed when the engine revolution speed is a predetermined value or less. For example, the FCCB control may be performed in an idling condition of the engine.
According to still another aspect of the present invention, the FCCB control may be performed when the vehicle running speed is a predetermined value or less.
In addition, the storage means may storage initial values that are set in a manufacturing process. The initial injection correction amount may be obtained in several situations that meets the condition in which the FCCB condition was not existent last time but is existent this time. For example, the initial injection correction amount may be obtained when the FCCB condition is established for the first time after start-up of the engine. For example, the initial injection correction amount may be obtained when the FCCB condition is established just after the engine has stared under cold condition after the engine has stopped under completely warmed-up condition. For example, the initial injection correction amount may be obtained when the FCCB condition is established after the vehicle has traveled just after the engine has started under a cold condition.